1. Field of the Invention
The present invention relates to composite materials for bone defect filling and bone replacement comprising organic material and inorganic material, more particularly to composite materials for bone defect filling and bone replacement wherein cyanoacrylate as organic material and bioactive osteo-conductive inorganic material as inorganic material are combined.
2. Description of the Related Art
Bone researches are investigated a lot in overall medical fields including dentistry and orthopedic surgery. Materials for bone replacement should have excellent tissue compatibility, be available in unlimited quantities, be easy contoured, retain stable shape over time, become ingrowth or replaced by living tissue. However, there is no material suitable for this use yet.
Presently, the bone replacement is conducted merely by implanting an autograft in a lesion lacking in bones. The bone autograft is most outstanding to bone regeneration. But, after operating the autograft, the prognosis is discriminated, depending upon lesion sites. That is to say, the autograft may not demonstrate its function properly due to histological differences in between donor site and acceptor site. Furthermore, the autograft is limited in the amount, if needed a lot. This operation may overburden on both the patient and manipulators, if repeated.
In order to find out another materials for implanting an autograft-like bone, allogenic or xenogenic bones are selected. The allograft or xenograft are not produced easily and may cause a histological rejection either. Therefore, bone researches start to investigate alloplastic bones or synthetic bones. For this purpose, almost all materials such as metal, organic material and ceramic are being examined, but not applied satisfactorily yet.
In detail, the metal refers to an implant using pure titanium alloy etc. The implant alloy is utilized to replace roots of teeth and plays a partial function of bone. However, this is limitedly used, when osseous injuries are less dense or wide. Thus, the metal alloy is still considered unsuccessful, because it cannot replace bones directly. Further, the metal alloy is lacking in sustaining the original shape of bone.
In addition, the organic material exemplifies polymethyl methacrylate (PMMA). However, the PMMA is problematic to cause cell necrosis because of polymerization heat and toxicity of monomer. Further, the organic material may cause the isolation of implant metals and adverse actions like a foreign body, if used for a long time, because it is hardly absorbed and replaced by bone. Vale, Vazquez, Vila and their collaborators have investigated to minimize the harmfulness, when the bone implant and adhesive material are used on a hip joint. Besides, Kawanabe has attempted to apply Bis-GMA(2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]propane) into bones. However, this study regarded bone adhesive material, like PMMAs either. In the plastic surgery, the PMMA is used to connect metals for replacing a hip joint to bones.
In addition, the inorganic material similar to the inorganic constituent of bones is cited. Brown et al. have examined porous hydroxyapatite (HA) for an absorbable inorganic material. Wolfe has elucidated that β-tricalcium phosphate (β-TCP) is degraded slowly so as to be replaced by new bones, since it has the same structure with the inorganic component of natural bone. Chow et al. have reported the osteo-conductivity of β-TCP. Also, Possets et al. have disclosed researches on tetracalcium phosphate and Frankenburg et al. have published studies on calcium phosphate cement and the like. In addition to simple bone cements, the bone cement mixture blending several inorganic materials, is investigated to be manufactured. This bone cement is made of viscous substance excluding a powered form to reduce the initial fluidity and maintains the shape in some extent. However, the result is not expected to satisfy all the needs. Most materials are often provided in a powder or have insufficient strength to be molded. Thus, their molding is hardly maintained and restricts the availability on lesion sites operated. Furthermore, the scaffold block used for implant is not easily manipulated to be adapted on a lesion.
These bioactive ceramic materials for bone regeneration described above are not osteo-inductive but osteo-conductive. Therefore, these ceramic materials are preferred to have a porous body containing proper pores connected and be permeated by bone tissue according to the growth. Further, they are required to adjust the biodegradation similar to the growth of new bones in their speeds. However, β-TCP is disadvantageous because it is to be utilized either in a powder or in a scaffold block reducing its strength.
Finally, the composite material combining inorganic material and organic material is being described. Raveh et al. have investigated to manufacture the composite material by using bioglass and Bis-GMA(2,2-bis[4(2-hydroxy-3-methacryloxypropoxy) phenyl]propane). However, this composite material is not absorbed completely and brings about adverse actions after operated. Especially, it is recognized as a foreign body due to lacking in adhesiveness. In addition, Wright et al. have contrived to prepare a composite material by mixing reinforcing fiber and PMMA. This composite material may disperse the heat of polymerization from PMMAs to prevent bone necrosis during the reaction. Nevertheless, this material has a too low adhesive strength as a glue to be applied actively. Mostly, these composite materials adopted non-absorbable substance and combined PMMAs matrix with inorganic material in order to improve the thermal property or resist during being cut. Commonly, the inorganic material is added in a ratio of 10 to 20%. Furthermore, Bank et al. started to synthesize composite materials by using hydroxyapatite (HA) and collagen and then, continue to manufacture the composite material by using HA and fibrin.
In order to settle above-mentioned problems, the present inventors have tried to prepare composite materials that maximize the merits of inorganic material and organic material and minimize their demerits. As a consequence, we have manufactured novel materials excellent in the physical property for bone replacement and bone defect filling, because the organic material has the maintenance of shape and the adhesive property and the bioactive inorganic material has the osteo-conductivity on new bones and completed the present invention successfully as follows.